Ceramic fan construction for heat treating furnaces



H. N. IPSEN Jan. 10, 1956 CERAMIC FAN CONSTRUCTION FOR HEAT TREATING FURNACES Filed July 1, 1954 \Mn i 2 Egg United States Patent '0 j CERAMIC FAN CONSTRUCTIQN FOR HEAT TREATING FURNACES Harold N. Ipsen, Rockford, Ill. Application July 1, 1954, Serial No. 440,660

3 Claims. (Cl. 266-5) The present invention relates to furnaces, such as those used in heat treating metal workpieces, in which the atmosphere is circulated about the work by a fan driven by a motor mounted on the exterior of the furnace. More particularly, the invention pertains to a furnace in which the fan is made of a ceramic material to withstand comparatively high temperatures.

The general object of the invention is to provide in a furnace of the above character a new and improved means for connecting the ceramic shaft of the fan and the shaft of the motor without the danger of breaking the rather fragile fan shaft.

A more detailed object is to connect the fan shaft and the motor shaft in such a way that the forces resulting from the connection act on the fan shaft in compression only.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings in which Figure l is a fragmentary transverse sectional view of a heat treating furnace utilizing the novel fan construction of the present invention.

Fig. 2 is an enlarged fragmentary sectional view taken along the line 22 in Fig. 1.

As shown in the drawings for purposes of illustration, the invention is embodied in a heat treating furnace 5 having a closed chamber 6 in which the metal workpieces to be treated are placed. The chamber is heated to the desired temperature by heating elements 7 which may be gas burner tubes extending vertically through the chamber along the sides thereof. The atmosphere within the treating chamber is circulated around and through a baffie 8, which encloses the workpieces, and across the work by a fan 9. The latter is disposed above the baflie and is a single piece molding comprising four vanes 10 radiating from a shaft 11 which projects through an opening 12 in the top wall 13 of the furnace and is adapted to turn about a vertical axis. In order to withstand the comparatively high temperatures to which the work is subjected, the fan 9, including both the vanes 10 and the shaft 11, is molded from a ceramic material.

The fan 9 is driven by an electric motor 14 secured to the top wall 13 and is disposed on the outside of the furnace 5 with the rotor or shaft 15 of the motor axially alined with and connected to the fan shaft 11. The upper end of the fan shaft is tapered to form a conical. portion 16 (Fig. 2) which is received and held in a mating flared recess 17 in the lower end of the motor shaft to join the shafts for rotation together. If desired, a Water jacket 18 may be formed integrally with the motor casing and project down into the top wall. of the furnace around the upper end of the fan shaft to cool the latter and prevent overheating of the motor bearings 19.

In accordance with the present invention, the fan shaft 11 is connected to the motor shaft 15 in a novel manner so as to join the two together without the danger of breaking the fan shaft even though the latter is composed 2,730,352 Patented Jan. 10, 1956 of a fragile ceramic material. To this end, advantage is taken of the fact that the ceramic material is comparatively strong in compression by arranging the connection between the two to compress the fan shaft against the motor shaft. This is achieved by projecting an elongated fastening element 20 down through the motor shaft and into the fan shaft and by providing the fastening element with a part 21 (Fig. 2) which acts upwardly on the fan shaft. In this way, the element 20 forces the conical portion 16 of the fan shaft into the recess 17 from below the latter and thereby the forces resulting from the connection act on the fan shaft only in compression.

Herein, both the motor shaft 15 and the fan shaft 11 are hollow, being formed with axially alined bores 22 and 23 respectively, and the fastening element is an elongated bolt with its head at the lower end and constituting the part 21. The latter engages an abutment 24 in the form of an inwardly facing shoulder made by reducing the diameter of the bore 23 adjacent the upper end of the fan shaft. The bolt 20 extends beyond the upper end of the motor shaft where it is threaded to receive a nut 25. The nut engages an abutment surface 26 on the motor shaft, which surface may be the upper end of this shaft, and thus, when the nut is tightened down on the bolt, it draws the bolt head 21 up against the shoulder 24. This compresses the tapered end portion 16 of the fan shaft between the head and the motor shaft and thereby joins the two shafts for rotation in unison.

It will be observed that the only forces the bolt 20 exerts on the fan shaft 11 tend to compress the tapered end 16 of the shaft between the head 21 and the motor shaft 15. Although the ceramic material from which the fan and its shaft are made is weak in tension, it is strong in compression and, since the arrangement described above utilizes this strength, there is little danger of the fan breaking. While the positions of the nut 25 and the head 21 may be reversed, it is advantageous to have the head within the fan shaft since this leaves the end of the bolt 20 projecting above the motor 14 Where it may be gripped as the nut is tightened. It is unnecessary, therefore, to insert a tool up through the bore 23 in the fan shaft to grip the bolt for this purpose.

I claim as my invention:

1. In a heat treating furnace, the combination of, a fan composed of ceramic material and having a shaft projecting outwardly through one wall of the furnace and having a tapered outer end, said shaft being hollow and formed with an internal shoulder facing inwardly away from said tapered end, a motor mounted on the exterior of the furnace and having a shaft alined with said fan shaft and formed with an axial bore flared at its lower end to receive said tapered end, an elongated bolt projecting through said bore and into said fan shaft and having an enlarged head on the lower end thereof engaging said shoulder, and a nut threaded on the outer end of said bolt and operable to compress said tapered end against said motor shaft thereby to connect the latter and said fan for rotation together.

2. In a heat treating furnace having an opening through one wall thereof, the combination of, a fan composed of ceramic material and disposed within said furnace, said fan including a hollow shaft projecting through said opening and having a tapered outer end, a power rotated shaft disposed exteriorly of said furnace in alinement with said fan shaft and having an axial bore flared at the lower end to receive said tapered end, a shoulder formed on said fan shaft and facing inwardly away from said tapered end, an outwardly facing abutment formed on said power shaft, an elongated element projecting through said here and into said fan shaft, and two members, one on the inner end of said element and engaging said shoulder and the other on the outer end of the element and engaging said abutment, one of said members being threaded on said element to compress said tapered end against said power shaft thereby to connect the latter and said fan for rotation together.

3. In a heat treating furnace having a hole through one wall thereof, the combination of, a hollow power driven shaft disposed exteriorly of said furnace and alined with said hole, a fan of ceramic material disposed within said furnace and having a hollow shaft projecting into said hole and formed with an inwardly facing in- 10 4 ternal abutment, said shafts having opposed and mating surfaces engaging each other, an elongated fastening elem ment projecting through said power driven shaft and into said fan shaft and having a part engaging said abutmerit, and means for drawing said part against said abutment thereby holding said surfaces together and connecting said power driven shaft and said fan for rotation together.

7 No references cited. 

